Green Party leaders in Norfolk and Suffolk have called for a referendum to take place on whether new devolution proposals are introduced to the region.
Councils in the two counties, as well as Cambridgeshire and Peterborough, have until the end of this month to decide whether they want to join a new combined authorities, with an elected mayor.
But, in an open letter to the head of the group negotiating the settlement, senior Green officials say the deal must be revised.
Richard Bearman and Mark Ereira-Guyer, the party’s group leaders on Norfolk and Suffolk County Councils, say a referendum should then take place next year.
If voters backed the measures, the new structures would then come into force the year after.
They said: “The proposed agreement lacks the legitimacy of public endorsement.
“Improved democratic engagement is essential if we are to build a stronger, more inclusive civil society.
“We are demanding a revised East Anglian devolution agreement which should be put to a public referendum.”
Last week, Andy Wood, the chairman of the leaders’ group who is heading the devolution talks, presented new proposals to the government, which would see separate authorities created for Norfolk and Suffolk and Cambridgeshire and Peterborough respectively.
Authorities who signed a draft devolution deal in March are expected to decide whether to continue in the process by the end of June.
But widespread opposition remains to the proposal for elected mayors and the Greens’ letter sets out its concerns on the structure.
They said: “The proposed area is too large and the needs of its citizens too diverse for one individual to represent effectively.
“An elected mayor would add a costly, additional level of top-down hierarchy to the region, and would in the first instance be accountable to Whitehall.
“Electing a single individual for such a large area would remove local people from local decision making. It is not a true decentralisation of power and we cannot support it.”